27 YEARS AGO IN IDPH HISTORY

Illinois suffered the nations worst epidemic of St. Louis encephalitis
in 1975, resulting in 578 cases and 47 deaths. It was the first major outbreak
of a mosquito-borne disease in the state since 1930, when malaria sickened more
than 300 Illinoisans.

Although the Department had anticipated and prepared for a small outbreak of
the disease, no one had imagined that Illinois would lead the nation in the
number of cases and deaths. One of the states first cases of St. Louis
encephalitis that year was an 8-year-old from Cook County. While it is believed
that the child was exposed to an infected mosquito during a trip to Greenville,
Miss., other cases, these originating in Illinois, were soon reported.

When it became apparent a few days before the Labor Day weekend that the
state was facing a major outbreak of St. Louis encephalitis, the Department
turned to the news media to inform the public and provided daily updates.
Agency director Joyce Lashof alerted physicians in the state and asked them to
order tests for arbovirus infections in patients with appropriate neurological
symptoms.

As the scope of the outbreak expanded, Dr. Lashof increased the
Departments response

team to more than 100 public health workers. Staff were pulled from other
areas of the agency and reassigned to the Division of Disease Control, where
they assisted in following up on positive lab results, transmitting information
from local health departments, collating data and writing summaries. Other
staff were reassigned to the virology lab to help with testing the 13,000
specimens that were processed during the outbreak.

Still, staff were strained: At the state and local level, many people
routinely worked 14- to 16-hour days, seven days a week, for the two months the
outbreak lasted. In fact, one technician slept on a cot in the lab in order to
save the time spent commuting.

Mosquito control, initiated and supervised by Department engineers and
sanitarians, helped to curb the outbreak. However, by the time the outbreak had
subsided in mid-October, St. Louis encephalitis had sickened residents in
two-thirds of the states 102 counties. Almost half of the cases occurred
in Cook County, an area where the disease had never before been identified.

The states first ever case of St. Louis encephalitis was recorded in
1932 in eastern Illinois, in Paris, the Edgar County seat. The following year
there were 185 cases, most of them in Madison, Morgan and St. Clair counties,
and 59 deaths. Across the Mississippi River, the city and county of St. Louis
reported 1,114 cases and 224 deaths. It was during this 1933 outbreak that the
virus was first isolated, identified and named.Other, smaller outbreaks
of St. Louis encephalitis have occurred in Illinois in 1955, 1964 and 1968.

In the wake of the 1975 outbreak, the Department moved quickly to establish
a mosquito- borne disease early warning system and, in 1976, hired an
arbovirologist to coordinate the effort. The surveillance system remains in
place today.

A complex network that is activated annually from May until Oct. 31 (or two
weeks after the first killing frost), the surveillance system draws information
from hundreds of persons throughout the state who monitor reports of suspect or
confirmed cases of encephalitis or other mosquito-borne diseases.

Infectious disease physicians, hospital laboratory directors and infection
control practitioners, local health departments and the Departments
laboratory, environmental health and communicable disease staffs test for and
report suspect or confirmed cases of aseptic meningitis, meningoencephalitis or
encephalitis, all of which can be caused by mosquito-borne viruses.

The system also relies on blood samples collected from wild bird
populations, mosquito pools and sentinel bird flocks that are screened for the
presence of mosquito-borne viruses.

Information gathered through these various sources guides prevention
activities, including public alerts that feature precautions on how to reduce
the risk of exposure to mosquitoes, such as wearing long pants and long-sleeved
shirts and using repellents appropriately. Other prevention efforts entail
cleaning up sites where tires are stored or discarded, requesting more
intensive surveillance by the states medical community and providing
guidance for mosquito control efforts at the local level.